/*
 * Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the OpenSSL license (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/* APIs and data structures for HPKE (RFC9180)  */
#ifndef OSSL_HPKE_H
#define OSSL_HPKE_H
#pragma once

#include <openssl/types.h>

/* HPKE modes */
#define OSSL_HPKE_MODE_BASE 0    /* Base mode  */
#define OSSL_HPKE_MODE_PSK 1     /* Pre-shared key mode */
#define OSSL_HPKE_MODE_AUTH 2    /* Authenticated mode */
#define OSSL_HPKE_MODE_PSKAUTH 3 /* PSK+authenticated mode */

/*
 * Max for ikm, psk, pskid, info and exporter contexts.
 * RFC9180, section 7.2.1 RECOMMENDS 64 octets but we have test vectors from
 * Appendix A.6.1 with a 66 octet IKM so we'll allow that.
 */
#define OSSL_HPKE_MAX_PARMLEN 66
#define OSSL_HPKE_MAX_INFOLEN 1024

/*
 * The (16bit) HPKE algorithm ID IANA codepoints
 * If/when new IANA codepoints are added there are tables in
 * crypto/hpke/hpke_util.c that must also be updated.
 */
#define OSSL_HPKE_KEM_ID_RESERVED 0x0000 /* not used */
#define OSSL_HPKE_KEM_ID_P256 0x0010     /* NIST P-256 */
#define OSSL_HPKE_KEM_ID_P384 0x0011     /* NIST P-384 */
#define OSSL_HPKE_KEM_ID_P521 0x0012     /* NIST P-521 */
#define OSSL_HPKE_KEM_ID_X25519 0x0020   /* Curve25519 */
#define OSSL_HPKE_KEM_ID_X448 0x0021     /* Curve448 */

#define OSSL_HPKE_KDF_ID_RESERVED 0x0000    /* not used */
#define OSSL_HPKE_KDF_ID_HKDF_SHA256 0x0001 /* HKDF-SHA256 */
#define OSSL_HPKE_KDF_ID_HKDF_SHA384 0x0002 /* HKDF-SHA384 */
#define OSSL_HPKE_KDF_ID_HKDF_SHA512 0x0003 /* HKDF-SHA512 */

#define OSSL_HPKE_AEAD_ID_RESERVED 0x0000        /* not used */
#define OSSL_HPKE_AEAD_ID_AES_GCM_128 0x0001     /* AES-GCM-128 */
#define OSSL_HPKE_AEAD_ID_AES_GCM_256 0x0002     /* AES-GCM-256 */
#define OSSL_HPKE_AEAD_ID_CHACHA_POLY1305 0x0003 /* Chacha20-Poly1305 */
#define OSSL_HPKE_AEAD_ID_EXPORTONLY 0xFFFF      /* export-only fake ID */

/* strings for suite components */
#define OSSL_HPKE_KEMSTR_P256 "P-256"             /* KEM id 0x10 */
#define OSSL_HPKE_KEMSTR_P384 "P-384"             /* KEM id 0x11 */
#define OSSL_HPKE_KEMSTR_P521 "P-521"             /* KEM id 0x12 */
#define OSSL_HPKE_KEMSTR_X25519 "X25519"          /* KEM id 0x20 */
#define OSSL_HPKE_KEMSTR_X448 "X448"              /* KEM id 0x21 */
#define OSSL_HPKE_KDFSTR_256 "hkdf-sha256"        /* KDF id 1 */
#define OSSL_HPKE_KDFSTR_384 "hkdf-sha384"        /* KDF id 2 */
#define OSSL_HPKE_KDFSTR_512 "hkdf-sha512"        /* KDF id 3 */
#define OSSL_HPKE_AEADSTR_AES128GCM "aes-128-gcm" /* AEAD id 1 */
#define OSSL_HPKE_AEADSTR_AES256GCM "aes-256-gcm" /* AEAD id 2 */
#define OSSL_HPKE_AEADSTR_CP "chacha20-poly1305"  /* AEAD id 3 */
#define OSSL_HPKE_AEADSTR_EXP "exporter"          /* AEAD id 0xff */

/*
 * Roles for use in creating an OSSL_HPKE_CTX, most
 * important use of this is to control nonce re-use.
 */
#define OSSL_HPKE_ROLE_SENDER 0
#define OSSL_HPKE_ROLE_RECEIVER 1

typedef struct
{
  uint16_t kem_id;  /* Key Encapsulation Method id */
  uint16_t kdf_id;  /* Key Derivation Function id */
  uint16_t aead_id; /* AEAD alg id */
} OSSL_HPKE_SUITE;

/**
 * Suite constants, use this like:
 *          OSSL_HPKE_SUITE myvar = OSSL_HPKE_SUITE_DEFAULT;
 */
#define OSSL_HPKE_SUITE_DEFAULT                                                \
  {OSSL_HPKE_KEM_ID_X25519, OSSL_HPKE_KDF_ID_HKDF_SHA256,                      \
   OSSL_HPKE_AEAD_ID_AES_GCM_128}

typedef struct ossl_hpke_ctx_st OSSL_HPKE_CTX;

OSSL_HPKE_CTX *OSSL_HPKE_CTX_new(int mode, OSSL_HPKE_SUITE suite, int role,
                                 OSSL_LIB_CTX *libctx, const char *propq);
void OSSL_HPKE_CTX_free(OSSL_HPKE_CTX *ctx);

int OSSL_HPKE_encap(OSSL_HPKE_CTX *ctx, unsigned char *enc, size_t *enclen,
                    const unsigned char *pub, size_t publen,
                    const unsigned char *info, size_t infolen);
int OSSL_HPKE_seal(OSSL_HPKE_CTX *ctx, unsigned char *ct, size_t *ctlen,
                   const unsigned char *aad, size_t aadlen,
                   const unsigned char *pt, size_t ptlen);

int OSSL_HPKE_keygen(OSSL_HPKE_SUITE suite, unsigned char *pub, size_t *publen,
                     EVP_PKEY **priv, const unsigned char *ikm, size_t ikmlen,
                     OSSL_LIB_CTX *libctx, const char *propq);
int OSSL_HPKE_decap(OSSL_HPKE_CTX *ctx, const unsigned char *enc, size_t enclen,
                    EVP_PKEY *recippriv, const unsigned char *info,
                    size_t infolen);
int OSSL_HPKE_open(OSSL_HPKE_CTX *ctx, unsigned char *pt, size_t *ptlen,
                   const unsigned char *aad, size_t aadlen,
                   const unsigned char *ct, size_t ctlen);

int OSSL_HPKE_export(OSSL_HPKE_CTX *ctx, unsigned char *secret,
                     size_t secretlen, const unsigned char *label,
                     size_t labellen);

int OSSL_HPKE_CTX_set1_authpriv(OSSL_HPKE_CTX *ctx, EVP_PKEY *priv);
int OSSL_HPKE_CTX_set1_authpub(OSSL_HPKE_CTX *ctx, const unsigned char *pub,
                               size_t publen);
int OSSL_HPKE_CTX_set1_psk(OSSL_HPKE_CTX *ctx, const char *pskid,
                           const unsigned char *psk, size_t psklen);

int OSSL_HPKE_CTX_set1_ikme(OSSL_HPKE_CTX *ctx, const unsigned char *ikme,
                            size_t ikmelen);

int OSSL_HPKE_CTX_set_seq(OSSL_HPKE_CTX *ctx, uint64_t seq);
int OSSL_HPKE_CTX_get_seq(OSSL_HPKE_CTX *ctx, uint64_t *seq);

int OSSL_HPKE_suite_check(OSSL_HPKE_SUITE suite);
int OSSL_HPKE_get_grease_value(OSSL_LIB_CTX *libctx, const char *propq,
                               const OSSL_HPKE_SUITE *suite_in,
                               OSSL_HPKE_SUITE *suite, unsigned char *enc,
                               size_t *enclen, unsigned char *ct, size_t ctlen);
int OSSL_HPKE_str2suite(const char *str, OSSL_HPKE_SUITE *suite);
size_t OSSL_HPKE_get_ciphertext_size(OSSL_HPKE_SUITE suite, size_t clearlen);
size_t OSSL_HPKE_get_public_encap_size(OSSL_HPKE_SUITE suite);
size_t OSSL_HPKE_get_recommended_ikmelen(OSSL_HPKE_SUITE suite);

#endif
